The present invention relates to a method of manufacturing various types of golf balls, such as one-piece golf balls and solid golf balls composed of a core enclosed by one or more cover layer. More specifically, the invention relates to a method of manufacturing golf balls in which, to inspect the surface of a ball-shaped molded material obtained after injection molding and to position markings thereon, the ball surface is placed in a reference orientation at a predetermined position.
Horizontally separating two-part molds have hitherto been used as molds for injection molding a cover resin material over a core in the manufacture of golf balls. When such a two-part mold is used, a seam line corresponding to the parting line of the mold appears on the golf ball.
This seam line is convenient for visually inspecting the golf ball and for applying markings to the ball. For example, flash normally forms at the seam line corresponding to the parting line of the two-part mold. When the mark left by the removal of such flash is to be inspected and processing is to be carried out on the ball, by specifying the position of the seam line and placing the ball in the inspection and processing apparatus, inspection and processing can be efficiently carried out. It is thus important to know where the seam line is located, and to position the ball accordingly.
When a marking such as lettering, a design or a trade mark is to be applied onto the seam line of a golf ball, it is essential to know the position of the seam line beforehand.
However, in recent golf balls, to make the arrangement of dimples formed on the surface of the ball as dense and uniform as possible so as to improve the aerodynamic properties and increase the distance of travel, it has become common practice to place a plurality of dimples across the parting line. This has made the seam line on the surface of the ball which corresponds to the parting line of the mold indistinct, so that it is often difficult to discern even when photographed with an image processing camera. Therefore, when inspecting processing of the seam line and inspecting pin marks left from molding, which are subsequent steps carried out after injection molding, it is difficult to accurately position the specific sites where the seam line or pin marks are located, thus compromising the efficiency of operations in the subsequent steps and resulting in a poor precision.
A golf ball is basically a sphere that lacks any distinguishing characteristic other than to be provided on the surface of the ball with dimples. Therefore, when a specific site on the ball's surface is to be inspected or a particular position is to be specified and a marking applied to that position, unless such an operation is carried out on the ball immediately after ball fabrication in the manufacturing process and before the ball is moved, it is difficult to re-locate the specific site. Hence, the environment for ball inspection and the like during the manufacturing process has been less than ideal.